Glass fiber spun rovings are known in the prior art and are used as reinforcement materials in various types of thermoplastic products, such as the types of glass fiber reinforced plastic products that are produced by the pultrusion process. Such reinforced thermoplastic products are used, for example, as sucker rods in oil well drilling because of their relatively light weight and good longitudinal direction strength. Most glass fiber spun rovings that have been used as reinforcement materials for such reinforced thermoplastic products have been produced by a process corresponding to that which is described in U.S. Pat. No. 2,795,926 (W. W. Drummond), which is assigned to the assignee of this application. As described in the aforesaid U.S. Pat. No. 2,795,926, a main strand of glass fiber is caused to form multiple loops therein by passing it through a spinner to form a roving-like article, and the roving-like article is then combined with a group of primary filaments into a composite product. This composite product is rather expensive to produce, due partly to the fact that the primary filaments are relatively expensive because of their relatively low bulkiness, and due partly to the fact that the process is awkward and is not readily adaptable to standard production techniques or high throughput bushings.
Due to problems relating to the use of primary filaments and to the awkward nature of the process that was associated with the manufacture of roving-like glass fiber products according to the teachings of the aforesaid U.S. Pat. No. 2,795,926, an alternative spun roving product, and method and apparatus for the manufacture thereof, was developed and U.S. Pat. No. 3,324,641 (G. E. Benson, et al.), also assigned to the assignee of this application, was granted thereon. According to U.S. Pat. No. 3,324,641, a spun roving glass fiber product can be produced without the need for a separate source of supply of primary filaments, by passing a strand through a peg wheel spinner to form multiple axially extending loops therein and then through a spinning, frustoconically shaped spinner, from the large end to the small end thereof, to cause the axially extending loops to intertwine and interlock with one another. However, the process of the aforesaid U.S. Pat. No. 3,324,641 was not effective in forming a spun roving glass fiber product with a significant number of cross-axial loops, and did not gain widespread commercial acceptance except in regard to the manufacture of decorative yarn. Further, the process of the aforesaid U.S. Pat. No. 3,324,641 employed an air tucker to direct high velocity air in an annular pattern against the product to enhance the texturizing of the product, which is an important characteristic in a decorative yarn product. However, it has been found that this air tucker frequently results in the fracturing of some of the loops of the product and this is a factor which detracts from the tensile strength of the product.